Production of nitric oxide in loam under aerobic and anaerobic conditions.

Measurements of gas flow through soil columns of loam from Kjettslinge, Uppland, Sweden, gave average NO production rates of 0.06 +/- 0.01 ng of NO N g of soil min in aerobic conditions and 3.7 +/- 0.6 ng of NO N g of soil min in anaerobic conditions at 25 degrees C. Approximately 30% of the NO(3) loss in anaerobic conditions was as NO. In aerobic conditions an equilibrium concentration for NO was found. Above this concentration there was uptake of NO. Autoclaved samples indicated that less than 10% of the NO production was abiological, and there was no abiological NO uptake. The NO production reached anaerobic rates at soil O(2) levels between 0.5 and 0.05%.